toomey



a? J. F. TOOMEY v SUBSCRIBER'S EQUIPMENT FOR PROGRAM TRANSMISSION Filed Dec 1, .1933

--2.x-- L -$wsm@ I, 'EN TOR JKI/Zamgg A TTORNEY program purposes and may be. disconnected.

Patented May 17,1927.

.U NITIED STAT -s1 PATENT orries;

JOHN F. TOOMEY, OF NEW YORK,1\T. Y., ASSIGLTOR *TO AMERICAN TEIJEPHONE AND TELEGRAPH COMPANY, A GORPORATIONOF NEW YORK.

SUBSCRIBERSEQUIPMENT FOR PROGRAM TRANSMISSION.

. Application filed December 1, 1923.. Serial No; 677,993.

This invention relates to programtrans-H mission over wires and. particularly to systems in which a programchannel, employing audio frequencies, is superposed 'upon an ordinary subscriber-s telephone line- It has been proposed. to use ordinary subscribers telephone lines for program purposes by transmitting program-currents over the lines at voice frequencies during such times as the telephone line is not being used for ordinary-telephonic purposes.-, Under such. circumstances it is desirablewthat the program system be so superposed on. the telephone line that the program apparatus *Will be disconnected either; when aJcall comes paratuslthat a low impedance loud speaker may be used at the subscribers station for automatically as soon as the.operator 'plugs into the subscribers line. The dlsconnecltion actually takes place before the line is.

at once ,lupon' taking the receiver from the switchhook ofthe telephone set.

vent the low impedance program receiving set from actuating thecentral office line equipment. It hasheretotore been proposed...

to accomplish this result by including acondenser in circuit with. the program. receiver;- As the use of such a'condenser produces; some distortion in the progran'i transmission, which is highly undesirable, particularly in the transmission of music, it is proposed in;

accordance with the. presentvinventton to accomplish thisresult by operating the-line signal equipment at the central office Over a simpler circuit. ceiving equipment is bridged. "across the line it .Will .not produce any effect uponwthe. simplex circuit. r Other and .i'urther objects oftheinvention willbe clear from the following description when read.- in connection withthe .accom-p panying drawing, the figureot which illus.-. trates a circuit arrangementembodying: a preterredtorm .of'ithe. invention.:.

Since: the: siiibsc'rib'efs re-.

Referring to the drawing, L designates a subseribefisline terminating in the usual subscriberls set 10. At the central oflice the line is connected over the back contacts of the cut-oti' relay CO and through a transformer 11. to; atrunk T leading to a program station. .A jack J is provided for establishing; connections to the telephone line L through the central office in the usual manner and aline lamp 12 is connected from the midpoint of the secondary of the transiiormerrl'l. to battery over a back contact of the jack J. The front contact of said jackis connected to the cut-off relay CO.

At the subscribefls station alow impedance loud speaker 13 is provided, this loud speaker being associated through a trans.

former 19 with a bridge circuit 17, through which the, loud speaker is connected-tothe line; 'llheabridge eircuitis controlled by the contact of a high resistance relay R,

which is connected over conductor 20 and the contact of a relay 21 to the midpoint of the primary of the transformer 19. A non locking key K is provided, Whose contacts 15 and 16 control the circuit from the relay Rte ground. AIdirectcircuit to ground, independent of the relay, may be established plveii' the contact 14- of the subscribers switch- The operationis as follows: When a sub 7 i f scriber desires to make an ordinary tele Another ob ect of the invention is'to1pre-l phone call he takes the. receiver from the switchhood, thereby closing a connection from ground, over the contact 1 1, over conductor 20, back contact of relay 21, through the upper half of the primarywinding of the transformer 19 and thence in parallel over the tip side oi? the line L, and through the subscribefls set over the ring side of the. .line L, thence over the back contacts of the cut-oil relay CO through the upper and lower halves of the primary Winding of the transformer 11 to the midpoint thereofand' from this point through. the line lamp 12 over the back. contact of the jack ,J to battery. The line lamp now glows and notifies the operator that a connection is de sired. The operator thereupon plugs into the ackal and disconnects battery from the disconnected from the trunk T and con nected to the tip and ring terminals of the jack J. The battery supply is now furnished to the line L over the tip and ring conductors of the jack J and the relay 21 is energized to open the connection so that the usual metallic telephone connection, independent of any grounds, is established.

If the subscriber desires to receive program transmission the non-locking key is actuated to mementarily close the contact 15 so that a circuit is established from ground. over the contact 16, contact 15, throu h the winding of the high resistance relay It, over the back contact of relay 21, over. the upper half of the primary winding of the transformer 19, over the tip side of the line, back contact of cut-off relay CC) throiwh the upper half of the primary winding 0 tra ns former 11 through the line lamp 12 and over the back contact of the jack J to battery. Owing to the high resistance of the relay R the line lamp 12 is not caused to glow but the relay R is energized and locked up over its front right-hand contact, independently of the contact 15. At its lefthand contact the relay R completes the bridge circuit 17 through the primary of.

the transformer 19 so that the loud speaking receiver 13 is nowbridged across the line L. While the resistance of the circuit, including the relay R and the line lamp L, is now somewhat reduced owing to the completion of a parallel circuit over the ring side of the line at the time the relay R was "energized, the resistance is not sufliciently reduced to permit the lam the resistance of the relay compared with the resistance of the line. Program transmission may now be received 12 to glow, as

from the program station throughthe translormer 11 and over the metallic line circuit through the transformer 19 to the loud speaker 13. The fact that the loud speaker is of low impedance has no effect to operate the line lamp as the loud speaker is in eluded in the circuit over the two sides of the line in series where the linelamp is" included in a circuit over the two sides of the line in parallel.

If, while the subscribers line is being used for program transmission, a call should come in for the subscriber the operator will insert the plug of her cord into the jack J,

thereby disconnecting battery from the circuit through the Line lamp 12 and over the 1 two sides of the line'L inparallel to the hand contact.

- is quite high as sire to initiate a call he removes his receiver from the switchhook and closes a circuit from ground over the contact 14 to the conductor 20. This short circuits the high resistance rela R, thereby deencrgizing said relay and at t e same time reducing the resistance of the circuit through the line lamp 12 so that the latter now glows. The relay R, upon being released, is unlocked so that it cannot be again actuated except by closing the con-' tact 15 and said relay disconnects the loud speaker from the line, as already described. Theoperator, u n observing the. line lamp 12, inserts a p ug in the jack J, thereby etfac-ing the line lamp and actuating the cut-off relay to disconnect the line L from the program trunk T and connect the line to the switching jack J.

While the circuit, as above illustrated, is especially applicable to private branch exchanges, it is equally applicable to ordinary telephone exchanges.

It will be obvious that the general principles herein disclosed may be embodied in many other organizations widely different from those illustrated without departing from the spirit of the invention as defined in the following claims.

What is claimed is:

1. Ina program system, a subscribers telephone line, means to connect said telephone line to a program station, switching terminals for said line, a line signal associated therewith, a low impedance program receiver for said line adapted to be bridged across the line, means to establish a circuit over thetwo sides of said line in parallel to operate said line signal, a relay controlling the connection of said program receiver to the line,.and.means to establish a circuit for said relay over the two sides of the line in parallel.

2. In a program system, a subscribers telephone line, means to connect said telephone line to a rogram station, switching terminals for said line, a line signal associated therewith, a low impedance program receiver for aaidline adapted to be bridged across the line, means to establish a circuitover the two sides of said line in parallel to operate said line signal, a relay controlling the connection of said program receiver to the line, and means to establish a circuit for said relay over the two sides of the line in parallel, the resistance of said relay being sufliciently high to prevent the operation of said line signal.

In a program system, a subscribers telephone line, means to connect said telephone lineto a program station, switching terminals for said line, a line signal associated therewith, a low impedance program receiver for said line adapted to be bridged across the line, means to establish a circuit over the two sides of said line in parallel to operate said line signal, a relay controlling the connection of said program receiver to the line, means to establish a circuit for said relay over the two sides of the line in parallel, the resistance of said relay being sufficiently high to prevent the operation of said line signal, means to lock up said relay when actuated by a subscriber, means for establishing a connection to the switching terminals at the central station, and means responsive to the establishment of such connection for releasing and locking said relay and for thereafter disconnecting the line from the program station and connecting it to the switching terminals.

4. In a program system, a subscribers telephone line, means to connect said line to a program station, switching terminals for said line, a line signal associated with said switching terminals, means for establishing a circuit to operate said line signal over the two sides of the line in parallel, a program receiver adapted to be associated with said line, means nnder thecontrol of the subscriber to bridge said receiver across the line in series, and means responsive to the establishment of a connection to said switching terminals at the central oflice for openin said bridge and thereafter connecting said line to the switching terminals.

In testimony whereof, I have signed m name to this specification this 30th day of November, 1923.

JOHN F, TOOMEY. 

